Abstract: The spheroidizing treatment principle and carbide spheroidizing mechanism of T12A carbon tool steel were discussed. The spheroidizing treatment parameters were optimized through typical spheroidizing treatment experiments. The results indicate that, after using a compound spherical annealing process of 770℃, the distribution of T12A carbon tool steel is dispersed, the grain size is 1.5-1.8 μm, and the hardness is 92-94 HRB.A practical spheroidization process is obtained, which has important reference value for the spheroidization of T12A carbon tool steel in high efficiency production.